Seshat

:warning: This is a complete rewrite of Seshat. If you're looking for the v1, please head to the v1 branch :warning:

See the Breaking Changes section for incompatibilities between v1 & v2.

Seshat provides a way to interact with storage (be it local, gcs, s3, ...) using HTTP while providing ways to implement things such as:

• access-control (not everyone can do the same things on objects)
• avoid file collision (many people want to upload files with the same name, they shouldn't override each other)
• transform files upon upload (compressing, image cropping, ...)
• async vs sync file processing upon uploads
• ...

How?

Seshat provides a series of middlewares and routers that can be used in any express app in order to serve/accept files.

Vocabulary

Most of the vocabulary used in seshat reuses concept shared by many cloud storage solution such as S3 and GCS such as Bucket and Object.

A Bucket is a storage place where Objects can be written. In Seshat, a Bucket can be backed by a local storage (your disk) an S3 Bucket, a GCS Bucket or even a certain prefix on an S3/GCS bucket.

Policies provides us with an easy way to implement things like access control, ready-only buckets or buckets that only accept a certain kind of objects.

Transformers allow us to transform objects as they are being uploaded or retrieved from a bucket. (eg. resize an image, compress files, ...)

Examples

Please have a look at the examples/ folder, you'll find simple examples showcasing:

• serving files from a local storage
• serving files from an S3 bucket
• use middlewares to ensure requests come from valid users
• use policies to make a bucket read-only
• rename objects as they are uploaded
• compress objects as they are uploaded
• create thumbnails from uploaded images
• create thumbnails on-the-fly when recovering files
• scan files for viruses using clamav
• encrypt files using SSE-C
• execute actions such as creating empty prefixes and extract objects as zip files

Breaking Changes

http protocol

Seshat v2's HTTP layer has some breaking changes compared to v1:

POST

• v1 supported multiple file uploads via multipart/form-data but never returned anything else than a 204 status code with a Location header with the first object's public url. v2 returns an actual JSON payload with an array of object metadata.